Vitamin A

Vitamin A is a group of fat-soluble nutrients, including retinol and provitamin A carotenoids, needed for vision, immune function, growth, and cell differentiation.

Retinal: Retinal is a vitamin A aldehyde that binds opsins and changes shape when it absorbs light. Its light-triggered shape change starts the visual signal in the retina.
Retinol: Retinol is an alcohol form of vitamin A found in animal foods and used in transport and metabolism. It is a preformed dietary form and a central intermediate in vitamin A metabolism.
Night blindness: Night blindness is impaired vision in dim light, often caused by vitamin A deficiency. Reduced retinal availability disrupts the visual cycle in rod cells.
Frederick Gowland Hopkins: Frederick Gowland Hopkins was a British biochemist who demonstrated the need for dietary accessory factors in animal growth. His work helped establish the scientific basis for recognizing vitamins, including vitamin A.
Vitamin D: Vitamin D is a group of fat-soluble nutrients that regulate calcium balance and support bone health. It shares fat solubility with vitamin A but has different principal functions and deficiency effects.
Rhodopsin: Rhodopsin is a light-sensitive pigment in rod cells, composed of opsin and 11-cis-retinal. Vitamin A supplies the retinal chromophore that rhodopsin needs to detect dim light.
Beta-carotene: Beta-carotene is a plant pigment that humans can convert into vitamin A. It is the best-known provitamin A carotenoid and a major dietary source.
Xerophthalmia: Xerophthalmia is a spectrum of eye disease caused by severe vitamin A deficiency, including dryness and corneal damage. It is the characteristic progression of deficiency-related eye injury.
Elmer McCollum: Elmer McCollum was an American biochemist who helped identify fat-soluble A in early nutrition experiments. His studies helped distinguish vitamin A from water-soluble growth factors.
Vitamin E: Vitamin E is a group of fat-soluble compounds that protect cell membranes from oxidative damage. It is another fat-soluble vitamin, but it does not supply retinoids or support the visual cycle.

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